The present invention relates to a pillar structure of a vehicle body provided with a pillar extending substantially in the vertical direction.
In the side of a vehicle body, a front pillar, a center pillar, and a rear pillar are disposed, in that order, from the vehicle front side. In the lower part of the center pillar, a seat belt retractor for retracting a seat belt is incorporated.
In recent years, there has been a tendency for the seat belt retractor, provided additionally with various safety devices, to increase in size. Accordingly, there has been a tendency for an opening formed in the center pillar incorporating the seat belt retractor to increase in size.
On the other hand, in order to facilitate passengers getting into and getting out of a rear seat, an opening on the rear door must have a large opening area. However, an increase in the opening area on the rear door decreases the width between an opening edge of the center pillar and an opening edge of the rear door, so that the strength of that portion is reduced, and there arises a large difference in strength between that portion and a portion above the opening. Therefore, in the case of the application of an impact load to the center pillar from the side at the time of side collision of a vehicle, a problem occurs in that a portion around the opening having a low strength of the center pillar is deformed greatly to the inside of a vehicle compartment.
Also, since a rear door hinge for supporting a rear door is attached to the vehicle rear side of the center pillar, the deformation (intrusion amount) of the lower part of the center pillar to the inside of the vehicle compartment at the time of side collision of the vehicle tends to increase, especially on the vehicle rear side.
JP 2002-120758 A discloses a technique for restraining the general deformation of the center pillar at the time of side collision of the vehicle by using a high tension steel material as an inner panel and inner reinforcing members of the center pillar.
Unfortunately, if a high tension steel material is used as the inner panel and inner reinforcing members of the center pillar as proposed in JP 2002-120758 A, there arises a problem in that the formability of the inner panel of the center pillar is deteriorated, and additionally the material cost and the working cost increase.
In order to keep the deformation of the center pillar at the time of side collision of a vehicle small, it is conceivable to use a structure in which the strength is increased by increasing the thickness of the inner panel. However, the increase in the thickness of the inner panel reinforces locations that do not require high strength, which poses a problem of excessively increased weight and cost.
It is also conceivable to use a structure in which the strength of the center pillar is increased by increasing the material strength without increasing the weight. However, the use of high-strength material as the inner panel having an intricate shape poses a problem of difficulty in working.